RAID Capacity Calculator
Fill in the values and the answer updates as you type.
How the RAID Capacity Calculator works
Usable space depends on the level: RAID 0 uses every disk, RAID 1 mirrors so you get one disk, RAID 5 loses one disk to parity, RAID 6 loses two, and RAID 10 keeps half. Minimum disk counts apply (3 for RAID 5, 4 for RAID 6 and RAID 10). RAID is not a backup. Example: with the default values, four 4 TB disks in RAID 5 give 12 TB usable.
Inputs and results
The RAID Capacity Calculator takes 3 inputs and gives 4 results.
What you enter
- RAID level — starts at RAID 5. Choose from: RAID 0, RAID 1, RAID 5, RAID 6 and RAID 10.
- Number of disks — starts at 4.
- Size of each disk (TB) — starts at 4.
What you get
- Usable capacity (TB)
- Raw capacity (TB)
- Storage efficiency
- Disk failures survived
Example: RAID Capacity Calculator with the starting values
With raid level RAID 5, number of disks 4 and size of each disk 4 TB, the calculator returns:
| Usable capacity (TB) | 12 |
|---|---|
| Raw capacity (TB) | 16 |
| Storage efficiency | 75% |
| Disk failures survived | 1 disk |
Change any value above and the results update straight away.
RAID Capacity Calculator FAQ
How do I use the RAID Capacity Calculator?
Enter raid level, number of disks and size of each disk in the fields, then read usable capacity (tb), raw capacity (tb), storage efficiency and disk failures survived in the result panel. The answer updates as you type, and you can press Calculate or Enter to refresh it. Use “Copy link” to share your exact numbers with someone else.
What does the RAID Capacity Calculator calculate?
Usable storage and fault tolerance for common RAID levels. It returns usable capacity (tb), raw capacity (tb), storage efficiency and disk failures survived from the 3 values you provide.
What values does the RAID Capacity Calculator start with?
It opens with raid level RAID 5, number of disks 4 and size of each disk 4 TB so you can see a working result straight away. Replace them with your own numbers, or press Reset to return to these starting values.
Is the RAID Capacity Calculator free and private?
Yes. It is free, needs no account, and runs in your browser, so nothing you type is sent to or stored on our servers. See the Privacy Policy for details.
Can I rely on the RAID Capacity Calculator for important decisions?
Treat the result as a well-rounded estimate. Real situations often have details a general calculator cannot know, so confirm important decisions with a qualified professional. See the Disclaimer for more.